computer continually rebooting

I am trying to get an old computer going for my neice but the machine which in the past has behaved normally now keeps rebooting after five or six seconds to perhaps a minute. However when this morning I put in the Windows 98SE startup floppy disc and arrived at the A:/ prompt I left the machine alone and it didn't reboot until after about 30 minutes. Just three days ago I did manage to reformat the disc, and load Windows 98SE without problems, but before and since then the problem still occurs. At the moment with the exception above it reboots after only a few seconds from swith on. I have cleaned the MB as best I can, the fan on the CPU is working, I have tried a different motor and tried to get it going with and without a graphics card being installed. I have also checked all leads and moved the 32mb memory stick to the slot nearest the CPU. The processor is an intel celeron 332mhz on an MS-6159 MB. Yes, it's an old machine but my wife uses an identical model with no problems at all and my neice is desperate for a unit to do homework on!

When I managed to load Windows 98SE three days ago I also loaded the latest version of the free AVG antivirus software from a disc and scanned the machine, no problems found. I have never been on-line with this machine. This software has also been loaded to another machine with no problems so is 'clean'.

From continual rebooting before managing to load Win 98SE etc. I hadn't touched anything in the machine so the 'fault' went away on its own accord for the time it took me to reformat the 6gb disc load Win98Se and the AVG programme.

Following this operation it still worked OK until the next day when I switched on. Seems to rule out heat?

Incidentally I can switch off the machine by holding in the 'on' switch for a few seconds but as soon as I release it the machine starts up again. If I remove the mains plug to stop the machine and then replace it the machine sometimes starts up without any switches being pressed.

Hi, I don't want to insult your intelligence, and perhaps this is being too simplistic but, when you shutdown in the normal way and you have the options to go on Standby, Restart or Shutdown - have you checked that it is not set to Restart? ......... Just a thought from very much a non-expert!! lol

This morning the machine managed to load windows through MS Scandisk to the desktop but then cut out again. Then, after a few 'nearly there' tries I managed to load windows into "safe mode". At the prompt I used "shut down" as normal and the machine shut down properly.

I then tried to use the power button as normal to get it started again but nothing happened for a few seconds and then it started up again spontaneously (with the same old problem). When it is trying to load pressing the reset or power button does nothing so perhaps the fault lies in these two switches but why does it sometimess stay on for a long time (when I managed to reformat etc. and at other times only for a few seconds?

Thanks for the advice Grouse I did exactly what you said re disconecting hard drive (I have no cards plugged in except a standard VGA Graphics card) and the machine booted up to a Boot Failure screen asking for a Boot diskette.

I left the machine in this state and the motor ran for ten minutes or so before stopping again. I repeated the bootup and this time the motor ran but the monitor took two or three minutes before it showed a signal. It just sat there with the anber light showing until eventually I got the green light and a signal. I did notice during this time that the motor appeared to hesitate for a mere fraction of a second a couple of times.

The switches seem to be working properly because I switched off by holding the on/off button for a second or so and then on again, and I have also tried the reset button.

I have now rebooted and I am at the Boot Failure screen again. This time the machine is running and I am letting it stay in this state to see how long it lasts.

Certainly having disconnected the hard drive there is a considerable improvement because before doing this it was only seconds before it rebooted. I shall report later after I see how long the present bootup lasts and then perhaps you will be able to tell me what to replace etc.